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Discussion Starter · #1 ·
I switched to a TH400 with a brake a couple of months ago. Due to various engine problems, I hadn't had the chance to play with the brake with a healthy engine until this past weekend. On Friday, I made three t-brake launches: 1.41, 1.43, 1.41. These were about 12-15# launches, not entirely sure, I was just getting the feel for it. The air was over 5000'.

On Saturday (same air), I footbraked for my class, and could do no better than 1.49, averaging ~ 1.52. Of course, launch boost was lower (5-7#). That accounted for the ET difference between the two days (9.70 @ 140 vs. 9.85 @ 140). The 60' variability is always the major problem for dialing in. With the brake, consistent staging position in the beams resulted in much less variability.

I tried a 20# plus launch during Sunday qualifying, but a problem ruined the launch/pass. For this car, consistent 1.38 or so is the goal.

Art
 

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That's pretty interesting, Art.


Were you launching off boost or rpm?

What ignition system are you using?



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Steve Wood

Growing old is mandatory; growing up is optional.


86 GN bought new, 87 T-type-81 El Camino with GN drive train-basically stock 86, 94 Caprice 9C1, 69 SS396 Camaro Convertible
 

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Discussion Starter · #3 ·
Well, I tell ya Steve, I have always gone by boost. I need to find the optimal sequence that is both quick to achieve (boost-wise)and reproducible. Additional electronics may be in order, and I hope I don't fry converters


I use the MSD DIS-4. I have no back-to-back data w/ and w/o it though. It ought to be useful for certain features I've yet to use. Todd turned me on to some colder NGK plugs for the GN1's, which I used for the first time in lieu of the Autolites.

Art
 

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It's an interesting subject....how to launch consistently.

You mentioned the air altitude and my first thought regarded the potential need to adjust launch boost and/or fueling for variations in "air" which led to my question regarding boost vs rpm.

I guess the MSD makes it easy to launch at the same rpm but then one has to figure what rpm is required each time to leave consistently, not mention what is required total boost/fuel-wise on the top end.

Sounds like a problem for Todd to me! *s*

We have come a long way since the flagman gave one car lengths over the other.
 

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Originally posted by Art Freeman:
I switched to a TH400 with a brake a couple of months ago. Due to various engine problems, I hadn't had the chance to play with the brake with a healthy engine until this past weekend. On Friday, I made three t-brake launches: 1.41, 1.43, 1.41. These were about 12-15# launches, not entirely sure, I was just getting the feel for it. The air was over 5000'.

On Saturday (same air), I footbraked for my class, and could do no better than 1.49, averaging ~ 1.52. Of course, launch boost was lower (5-7#). That accounted for the ET difference between the two days (9.70 @ 140 vs. 9.85 @ 140). The 60' variability is always the major problem for dialing in. With the brake, consistent staging position in the beams resulted in much less variability.

I tried a 20# plus launch during Sunday qualifying, but a problem ruined the launch/pass. For this car, consistent 1.38 or so is the goal.

Art


I wish you could have made the T-brake and foot-brake tests on the same day, that would have made the results a little more verifiable. As it is, there's too many variables, track condition, weather, etc. but mainly track condition, even different lanes will yield different results.



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TurboDave & Kathy Huinker, mailto:[email protected][email protected]</A>
TurboD Racing,BGNRA San Diego,GSCA-5311,Turbo Buick Web Ring
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86 GN(MM/MAF Xlator/Extender,MM BstC Boost Command,THDP,PTE44,CAS V2FM,MSD50's,9.5"vigilante 3500)
87 GN [email protected](Stock)
84 L69 Z28
 

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Discussion Starter · #6 ·
Originally posted by TurboDave:

I wish you could have made the T-brake and foot-brake tests on the same day, that would have made the results a little more verifiable. As it is, there's too many variables, track condition, weather, etc. but mainly track condition, even different lanes will yield different results.
Design: Yeah, me too, that would be nice. The primary goal of the weekend wasn't to make this comparison, or else I would have done as you suggest. I'm not staking my reputation as a scientist on the (non)experimental design, and I hope it didn't come across that way.
"Alls I know" is that I had never achieved a 60' close to 1.41 at this track in 7 years.

Lane Choice: I always make test and tune runs (i.e., when no eliminations follow) in the same lane on a given night. But I had more important fish to fry than A/Bing launch technique... such as resetting the track record for full-bodied V6


I only footbraked the next day because that's required in the class I run. I will soon ditch that and move up to SuperPro, where I can use the brake here.

Track Conditions: Definitely not the same. The tranny brake launches were made on test and tune night, where track prep is minimal and the bulk of the cars mess up the starting line with their street radials. The footbrake launches were race day after the starting line and track were sprayed.

Weather Conditions: this can easily vary from one run to the next, let alone day-to-day. That's why I keep a record of several parameters. This is useful in retrospective analysis of the effects of weather conditions with a database of hundreds of runs. Anyway, getting off-topic here...

I don't anticipate having the luxury to make a better comparison of this question with an acceptable "N". Not that important to me really. Just thought I'd share some of the results from my wall-to-wall weekend at the track.

Art
 

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My degree was in Meterology, Art...I will come run the weather station for you!



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Steve Wood

Growing old is mandatory; growing up is optional.


86 GN bought new, 87 T-type-81 El Camino with GN drive train-basically stock 86, 94 Caprice 9C1, 69 SS396 Camaro Convertible
 

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I believe that is the study of your mouth.
 

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Someone needs to develope (or maybe they already do?) an adjustable two stage boost control along with the adjustable 2 stage rev limiter. Each system should be adjustable independant of each other so someone can launch with more RPM than boost if needed or the other way around. Sounds like this should be easy to do.

KS

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87GN, 12.05 @ 111, SIXTY FOOT 1.60-LAUNCH 15#, BONE STOCK LONG BLOCK, STOCK I.C. (BELL MOUTHED), STOCK TRANS/CONV, Stock Turbo, 009'S, RED'S 107 CHIP. HOME MADE 3" DOWN PIPE. RUNS CONSISTANT 12.10'S-12.11'S.

http://www.geocities.com/kdslaby/solidworks.html
 

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Discussion Starter · #12 ·
Originally posted by lazaris:
I wonder how close the 60' would have been if you footbraked it to same psi as you did from the trans brake??????
The drivetrain physicists among us ought to clear this one up LOL! Also, position in the beams will obviously influence 60' (i.e., shallow lets you take a run at the lights). So, if you really want to start to cover the variables, in addition to weather conditions, track condition and temperature, rpm, boost, car position (in beams and left-right), tire pressures, etc., all have to be controlled for. It's fascinating but can easily fail my cost/benefit analysis


So the technical question remains, but I'd guess the answer has been known for years in the racing world. I do know that I'd never be able to hold 20# on the footbrake anyway.

Art
 

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The tranny brake would/should be faster as it will shock the tires harder as there is no pre-load applied as is the case with the foot brake.

Akin to leaving with a bit less than fall stall to flash the converter higher, I think.

The above is opinion as I do not even play a drive train expert on tv.
 

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Technically when you add a trans brake the rear suspension Percentage of Rise (PR) should be lowered. This will help the 60' and launch the car more efficently.
I'd guess your making enough power to get 1.33-1.35 60' times. The weight and gearing, suspension, etc needs to be factored but at this point I don't see why that would be a problem.

I do play an amature suspension guru on the weekends.


S.G. Kevin


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87GN, 12.05 @ 111, SIXTY FOOT 1.60-LAUNCH 15#, BONE STOCK LONG BLOCK, STOCK I.C. (BELL MOUTHED), STOCK TRANS/CONV, Stock Turbo, 009'S, RED'S 107 CHIP. HOME MADE 3" DOWN PIPE. RUNS CONSISTANT 12.10'S-12.11'S.

http://www.geocities.com/kdslaby/solidworks.html

[This message has been edited by KEVINS (edited August 02, 2001).]

[This message has been edited by KEVINS (edited August 02, 2001).]
 

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Revenge is a dish that often poisons the chef. Wait, your momma already tried that! Hmmmmmmm
 

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I understand...I was trying to say that I thought the tranny brake would be quicker, still, if boost levels were the same for both.


It might take more chassis preloading for the tranny brake than without, as well.

Be interesting to have scales under all four wheels to record load transfer.
 

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Actually I am an engineering designer.. We always joke that engineers aren't suppose to spell correctly


One of many faults that I have aquired from poor breeding. I'm still trying to breed in the correct qualities tho..


KS
 

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Originally posted by KEVINS:
Actually I am an engineering designer.. We always joke that engineers aren't suppose to spell correctly


One of many faults that I have aquired from poor breeding. I'm still trying to breed in the correct qualities tho..


KS
I resent that stereotype.
I'm an electronics engineer, and you can ask the people on IRC about my propensity to correct people's spelling; I'm known as "Webster".

It's "supposed" and "acquired", by the way...





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Orange Park, FL
various cars, some running
 
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